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燃煤发电是我国工业用水和排水量很大的行业，且大部分燃煤电厂地处生态环境脆弱、水资源匮乏的西北部地区。电厂经湿法脱硫而产生的脱硫废液含有较高浓度的盐、重金属、悬浮物等污染因素，是目前电厂比较难处理的废水。对燃煤电厂的水网络进行合理的规划设计，并对脱硫废液处理关键技术进行研究对电厂节水减排具有重要意义。本研究通过对陕西某大型电厂全局水网络调研，对电厂各用水和排水单元的水质、水量进行分析，绘制得出水平衡图。应用水夹点技术对电厂现有的水网络进行优化，实现新鲜水消耗量和废水排放量的减少。在水网络优化的基础上，以全厂废水零排放为目标，针对水网络中的零排放关键节点设计废水回用处理环节，再次优化电厂用水系统，极大降低新鲜水的消耗量并实现废水的零排放。针对电厂废水回用处理环节中的关键废水—脱硫废液，利用纳滤膜的分盐特性对其资源化处理展开研究。首先，考虑到电厂现有脱硫废液高钙、高镁的水质特征易对纳滤膜造成污染、影响分离效率，研究了脱硫废液膜处理前的软化工艺。研究中分别比较了Ca(OH)2-Na2CO3软化体系与NaOH-Na2CO3软化体系的处理效果与经济性，并考察了部分脱镁对于废水软化效果与经济性的影响规律。最终获得优化的脱硫废水软化预处理工艺。其次，对脱硫废液的纳滤分盐进行深入研究。考察了目前市面上最常用的四种商用纳滤膜（DL、DK、NF90和NF1）对硫酸根（SO42-）和氯离子（Cl-）的分离效率，并择优考察了溶液性质和操作条件对膜分盐的影响。研究显示，DL膜相比其他三种膜的膜通量与离子分离效率更高。降低溶液pH、增加离子强度有助于纳滤膜的离子分离效率的提高。pH、离子强度的增加会使得膜通量下降。纳滤膜的分离效率随阳离子价态的升高而变差。流速和压力的增大，可以在一定幅度上提高膜通量，却不利于离子的分离。;Coal-fired power generation is an industry with a large amount of water and waste water in China. The local ecological environment of the place, which most coal-fired power plants located, is weak and the water resources are scarce. It is of great significance to plan and design the water and wastewater treatment of coal-fired power plants, where water resources are scarce. Desulfurization waste liquid is one of the most difficult treatment wastewater because of its high concentration of salt, heavy metals, suspended solids and other pollutants. Water network optimization and desulfurization waste liquid treatment technology are the keys to water saving and emission reduction in power plant.In this work, a large power plant in Shanxi province was selected as the research object. Through the investigation of the global water network of the large power plant, the water quality and quantity of the water and drainage units were analyzed. A water balance diagram was drawn.The existing water network was optimized by using water pinch technology to reduce the discharge of fresh water and wastewater. Based on the optimization of water network, aiming at the zero discharge of wastewater, the plant water network was deeply optimized, through designing waste water treatment process.The reuse treatment of desalination waste liquid was studied by using the salt separation characteristic of nanofiltration membrane. Firstly, Considering the characteristics of high calcium and magnesium quality of desulphurization wastewater, which is easy to pollute the membrane and affect the separation efficiency, the optimum softening process of desulfurization waste liquor before membrane treatment was studied. In the study, the treatment efficiency and economy of Ca(OH)2-Na2CO3 softening system and NaOH-Na2CO3 softening system were compared. The effect of partial magnesium removal on the softening efficiency and economy of wastewater was investigated. Finally, the optimized softening treatment process of desulfurization wastewater was obtained.Secondly, the salt separation characteristic of nanofiltration membrane ,which was used to treat desulfurization waste liquor, was studied in depth. The separation efficiency of four kinds of commercial nanofiltration membranes (DL, DK, NF90 and NF1) for sulfate and chloride were investigated. The effects of solution properties and operating conditions on the separation performance of the membranes were investigated. The results showed the membrane flux and ion separation efficiency of DL were higher than the other three nanofiltration membranes. Decreasing the pH of solution and increasing ionic strength could improve the ion separation efficiency of nanofiltration membrane. The increase of ionic strength and pH leaded to the decrease of membrane flux. The separation efficiency of nanofiltration membrane is decreased with the increase of cationic valence state. The increase of flow rate and pressure increased membrane flux, and it wasn’t conducive to ion separation.
|刘佳音. 基于全局水网络优化的电厂高盐脱硫废液资源化处理关键技术研究[D]. 中国科学院研究生院,2018.|
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